Turbine rotor blade platform cooling

ABSTRACT

A cooling arrangement in a platform in a rotor blade or a sidewall in a stator blade in a turbine of a combustion turbine engine is described. The cooling arrangement may include: a cooling chamber configured to pass coolant from an inlet to an outlet; and a rib positioned within the cooling chamber. The rib may partially divide the cooling chamber so to form a switchback. The rib may be canted with respect to the cooling chamber such that the switchback has an ever narrowing channel.

BACKGROUND OF THE INVENTION

The present application relates generally to combustion turbine engines, which, as used herein and unless specifically stated otherwise, includes all types of combustion turbine engines, such as those used in power generation and aircraft engines. More specifically, but not by way of limitation, the present application relates to apparatus, systems and/or methods for cooling the platform region of turbine rotor blades and the sidewall region of turbine stator blades.

A gas turbine engine typically includes a compressor, a combustor, and a turbine. The compressor and turbine generally include rows of airfoils or blades that are axially stacked in stages. Each stage typically includes a row of circumferentially spaced stator blades, which are fixed, and a set of circumferentially spaced rotor blades, which rotate about a central axis or shaft. In operation, the rotor blades in the compressor are rotated about the shaft to compress a flow of air. The compressed air is then used within the combustor to combust a supply of fuel. The resulting flow of hot gases from the combustion process is expanded through the turbine, which causes the rotor blades to rotate the shaft to which they are attached. In this manner, energy contained in the fuel is converted into the mechanical energy of the rotating shaft, which then, for example, may be used to rotate the coils of a generator to generate electricity.

Referring to FIGS. 1 and 2, turbine rotor blades 100 generally include an airfoil portion or airfoil 102 and a root portion or root 104. The airfoil 102 may be described as having a convex suction face 105 and a concave pressure face 106. The airfoil 102 further may be described as having a leading edge 107, which is the forward edge, and a trailing edge 108, which is the aft edge. The root 104 may be described as having structure (which, as shown, typically includes a dovetail 109) for affixing the blade 100 to the rotor shaft, a platform 110 from which the airfoil 102 extends, and a shank 112, which includes the structure between the dovetail 109 and the platform 110.

As illustrated, the platform 110 may be substantially planar. More specifically, the platform 110 may have a planar topside 113, which, as shown in FIG. 1, may include an axially and circumferentially extending flat surface. As shown in FIG. 2, the platform 110 may have a planar underside 114, which may also include an axially and circumferentially extending flat surface. The topside 113 and the bottom side 114 of the platform 110 may be formed such that each is substantially parallel to the other. As depicted, it will be appreciated that the platform 110 typically has a thin radial profile, i.e., there is a relatively short radial distance between the topside 113 and the bottom side 114 of the platform 110.

In general, the platform 110 is employed on turbine rotor blades 100 to form the inner flow path boundary of the hot gas path section of the gas turbine. The platform 110 further provides structural support for the airfoil 102. In operation, the rotational velocity of the turbine induces mechanical loading that creates highly stressed regions along the platform 110 that, when coupled with high temperatures, ultimately cause the formation of operational defects, such as oxidation, creep, low-cycle fatigue cracking, and others. These defects, of course, negatively impact the useful life of the rotor blade 100. It will be appreciated that these harsh operating conditions, i.e., exposure to extreme temperatures of the hot gas path and mechanical loading associated with the rotating blades, create considerable challenges in designing durable, long-lasting rotor blade platforms 110 that both perform well and are cost-effective to manufacture.

One common solution to make the platform region 110 more durable is to cool it with a flow of compressed air or other coolant during operation, and a variety of these type of platform designs are known. However, as one of ordinary skill in the art will appreciate, the platform region 110 presents certain design challenges that make it difficult to cool in this manner. In significant part, this is due to the awkward geometry of this region, in that, as described, the platform 110 is a periphery component that resides away from the central core of the rotor blade and typically is designed to have a structurally sound, but thin radial thickness.

To circulate coolant, rotor blades 100 typically include one or more hollow cooling passages 116 (see FIGS. 3, 4, 5, and 9) that, at minimum, extend radially through the core of the blade 100, including through the root 104 and the airfoil 102. As described in more detail below, to increase the exchange of heat, such cooling passages 116 may be formed having a serpentine path that winds through the central regions of the blade 100, though other configurations are possible. In operation, a coolant may enter the central cooling passages via one or more inlets 117 formed in the inboard portion of the root 104. The coolant may circulate through the blade 100 and exit through outlets (not shown) formed on the airfoil and/or via one or more outlets (not shown) formed in the root 104. The coolant may be pressurized, and, for example, may include pressurized air, pressurized air mixed with water, steam, and the like. In many cases, the coolant is compressed air that is diverted from the compressor of the engine, though other sources are possible. As discussed in more detail below, these cooling passages typically include a high-pressure coolant region and a low-pressure coolant region. The high-pressure coolant region typically corresponds to an upstream portion of the cooling passage that has a higher coolant pressure, whereas the low-pressure coolant region corresponds to a downstream portion having a relatively lower coolant pressure.

In some cases, the coolant may be directed from the cooling passages 116 into a cavity 119 formed between the shanks 112 and platforms 110 of adjacent rotor blades 100. From there, the coolant may be used to cool the platform region 110 of the blade, a conventional design of which is presented in FIG. 3. This type of design typically extracts air from one of the cooling passages 116 and uses the air to pressurize the cavity 119 formed between the shanks 112/platforms 110. Once pressurized, this cavity 119 then supplies coolant to cooling channels that extend through the platform 110. After traversing the platform 110, the cooling air may exit the cavity through film cooling holes formed in the topside 113 of the platform 110.

It will be appreciated, however, that this type of conventional design has several disadvantages. First, the cooling circuit is not self-contained in one part, as the cooling circuit is only formed after two neighboring rotor blades 100 are assembled. This adds a great degree of difficulty and complexity to installation and pre-installation flow testing. A second disadvantage is that the integrity of the cavity 119 formed between adjacent rotor blades 100 is dependent on how well the perimeter of the cavity 119 is sealed. Inadequate sealing may result in inadequate platform cooling and/or wasted cooling air. A third disadvantage is the inherent risk that hot gas path gases may be ingested into the cavity 119 or the platform itself 110. This may occur if the cavity 119 is not maintained at a sufficiently high pressure during operation. If the pressure of the cavity 119 falls below the pressure within the hot gas path, hot gases will be ingested into the shank cavity 119 or the platform 110 itself, which typically damages these components as they were not designed to endure exposure to the hot gas-path conditions.

FIGS. 4 and 5 illustrate another type of conventional design for platform cooling. In this case, the cooling circuit is contained within the rotor blade 100 and does not involve the shank cavity 119, as depicted. Cooling air is extracted from one of the cooling passages 116 that extend through the core of the blade 110 and directed aft through cooling channels 120 formed within the platform 110 (i.e., “platform cooling channels 120”). As shown by the several arrows, the cooling air flows through the platform cooling channels 120 and exits through outlets in the aft edge 121 of the platform 110 or from outlets disposed along the suction side edge 122. (Note that in describing or referring to the edges or faces of the rectangular platform 110, each may be delineated based upon its location in relation to the suction face 105 and pressure face 106 of the airfoil 102 and/or the forward and aft directions of the engine once the blade 100 is installed. As such, as one of ordinary skill in the art will appreciate, the platform may include an aft edge 121, a suction side edge 122, a forward edge 124, and a pressure side edge 126, as indicated in FIGS. 3 and 4. In addition, the suction side edge 122 and the pressure side edge 126 also are commonly referred to as “slashfaces” and the narrow cavity formed therebetween once neighboring rotor blades 100 are installed may be referred to as a “slashface cavity”.)

It will be appreciated that the conventional designs of FIGS. 4 and 5 have an advantage over the design of FIG. 3 in that they are not affected by variations in assembly or installation conditions. However, conventional designs of this nature have several limitations or drawbacks. First, as illustrated, only a single circuit is provided on each side of the airfoil 102 and, thus, there is the disadvantage of having limited control of the amount of cooling air used at different locations in the platform 110. Second, conventional designs of this type have a coverage area that is generally limited. While the serpentine path of FIG. 5 is an improvement in terms of coverage over FIG. 4, there are still dead areas within the platform 110 that remain uncooled. Third, to obtain better coverage with intricately formed platform cooling channels 120, manufacturing costs increase dramatically, particularly if the cooling channels having shapes that require a casting process to form. Fourth, these conventional designs typically dump coolant into the hot gas path after usage and before the coolant is completely exhausted, which negatively affects the efficiency of the engine. Fifth, conventional designs of this nature generally have little flexibility. That is, the channels 120 are formed as an integral part of the platform 110 and provide little or no opportunity to change their function or configuration as operating conditions vary. In addition, these types of conventional designs are difficult to repair or refurbish.

In certain cases, platform cooling passages are configured with a switchback configuration. Example of such a design is shown in FIG. 6. As shown, the switchback design may include a cooling chamber 130 that includes an inlet 132 and an outlet 134, and a rib 135 that divides the chamber 130 such that coolant is forced to travel a circuitous route before reaching the outlet 134. In this manner, the coolant is exposed to the entirety of the cooling chamber 130 so that it may convectively cool the surrounding region. One shortcoming of this type of switchback is that the coolant absorbs heat as it moves through the switchback so that the downstream section receives less cooling than upstream sections, which causes uneven cooling through the platform and the development of component damaging hotspots. It will further be appreciated that the aforementioned issues with rotor blade platform cooling are applicable to sidewall regions within turbine stator blades.

As a result, conventional designs of rotor blade platform and stator blade sidewall cooling configurations are lacking in one or more important areas. There remains a need for improved apparatus, systems, and/or methods that effectively and efficiently cool these blade regions, while also being cost-effective to construct, flexible in application, and durable.

BRIEF DESCRIPTION OF THE INVENTION

In one exemplary embodiment, the present application describes a cooling arrangement in a platform in a rotor blade in a turbine of a combustion turbine engine. The cooling arrangement may include: a cooling chamber configured to pass coolant from an inlet to an outlet; and a rib positioned within the cooling chamber. The rib may partially divide the cooling chamber so to form a switchback. The rib may be canted with respect to the cooling chamber such that the switchback comprises an ever narrowing channel.

The present application further describes a cooling arrangement in a sidewall in a stator blade in a turbine of a combustion turbine engine. The cooling arrangement may include: a cooling chamber configured to pass coolant from an inlet to an outlet; and a rib positioned within the cooling chamber. The rib may partially divide the cooling chamber so to form a switchback. The rib may be canted with respect to the cooling chamber such that the switchback comprises an ever narrowing channel.

These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more completely understood and appreciated by careful study of the following more detailed description of exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a perspective view of an exemplary turbine rotor blade in which embodiments of the present invention may be employed;

FIG. 2 illustrates an underside view of a turbine rotor blade in which embodiments of the present invention may be used;

FIG. 3 illustrates a sectional view of neighboring turbine rotor blades having a cooling system according to conventional design;

FIG. 4 illustrates a top view of a turbine rotor blade having a platform with interior cooling channels according to conventional design;

FIG. 5 illustrates a top view of a turbine rotor blade having a platform with interior cooling channels according to an alternative conventional design;

FIG. 6 illustrates a top with partial cross-sectional view of a turbine rotor blade having a platform with interior cooling channel having a switchback configuration according to a conventional design;

FIG. 7 illustrates a top with partial cross-sectional view of a platform of a turbine rotor blade having a cooling configuration according to an exemplary embodiment of the present invention;

FIG. 8 is a side cross-sectional view along line 8-8 of FIG. 7;

FIG. 9 illustrates a top with partial cross-sectional view of a platform of a turbine rotor blade having a cooling configuration according to an alternative embodiment of the present invention;

FIG. 10 illustrates a top with partial cross-sectional view of a platform of a turbine rotor blade having a cooling configuration according to an alternative embodiment of the present invention;

FIG. 11 illustrates a top with partial cross-sectional view of a platform of a turbine rotor blade having a cooling configuration according to an alternative embodiment of the present invention;

FIG. 12 illustrates a graph depicting “Flow Parameters” against “Total Flow Distance Through Switchback” according to experimental data on embodiments of the present invention;

FIG. 13 illustrates a side view of a turbine stator blade showing the positioning of cooling configuration according to an alternative embodiment of the present invention; and

FIG. 14 illustrates a top with partial cross-sectional view of a sidewall of a turbine stator blade having a cooling configuration according to an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As discussed above, various conventional designs of internal cooling passages 116 are somewhat effective at cooling certain regions within a rotor blade 100. However, as one of ordinary skill in the art will appreciate, the platform region proves more challenging. This is due, at least in part, to the platform's awkward geometry—i.e., its narrow radial height and the manner in which it juts away from the core or main body of the rotor blade 100. Nevertheless, given its exposures to the extreme temperatures of hot gas path and high mechanical loading, the cooling requirements of the platform 110 are considerable. As described above, conventional platform cooling designs are ineffective because they fail to address the particular challenges of the region, are inefficient with their usage of coolant, and/or are costly to fabricate. It will be further appreciated that the sidewalls of stator blades present similar issues and deficiencies with conventional approaches, which will be discussed in more detail in relation to FIGS. 12 and 13,

Several particular descriptive terms may be used to describe exemplary embodiments of the present application. The meaning for these terms shall include the following definitions. The terms “downstream” and “upstream” are terms that indicate a direction relative to the flow of working fluid through the turbine or, as the case may be, coolant through a cooling passage. Accordingly, the term “downstream” means the direction of the flow, and the term “upstream” means in the opposite direction of the flow. The term “radial” refers to movement or position perpendicular to an axis. It is often required to describe parts that are at differing radial positions with regard to this axis. In these cases, if a first component resides closer to the axis than a second component, it may be stated herein that the first component is either “inboard” or “radially inward” of the second component. If, on the other hand, the first component resides further from the axis than the second component, it may be stated herein that the first component is “outboard” or “radially outward” of the second component. The term “axial” refers to movement or position parallel to an axis. And, the term “circumferential” refers to movement or position around an axis. Unless otherwise stated, when the terms “radial”, “axial”, or “circumferential” are used, they are used in reference to the central axis of the turbine engine.

Referring now to FIGS. 7 through 11, several views of exemplary embodiments of the present invention are provided. In particular, rotor blades 100 having a platform cooling configuration 130 according to preferred embodiments of the present invention are illustrated. As shown, the rotor blade 100 includes a platform 110 residing at the interface between an airfoil 102 and a root 104. A cooling chamber 130 may be formed within the platform 110. For example, as illustrated in FIG. 7, the cooling chamber 130 may be positioned near the forward edge 124 of the platform 110. The cooling chamber 130 may include an inlet 132 and an outlet 134. The inlet 132 may be supplied with coolant through a variety of ways, such as through an internal coolant passageway through the rotor blade 110 or via the shank cavity 119. During operation, a coolant may be directed through the cooling chamber 130, traveling from an inlet 132 to an outlet 134. A rib 135 may be positioned within the cooling chamber 130. The rib 135 may be configured to partially divide the cooling chamber 130 so that a serpentine or switchback path (hereinafter “switchback 131”) is formed. As discussed in more detail below, the rib 135 may be canted with respect to the cooling chamber 130. According to embodiments of the present invention, the rib 135 may be canted at an angle so that the switchback 131 has an ever narrowing channel.

In certain preferred embodiments, the ever narrowing channel of the present invention is one that narrows at a constant rate as it extends from the inlet 132 to the outlet 134 of the cooling chamber 130. In other preferred embodiments, the ever narrowing channel, as used herein, is defined as a channel that narrows at a constant rate along both of the flanks of the rib 135. More specifically, the switchback 131 may be described as having a pass positioned on each flank of the rib 135. These passes may be referred to as: an upstream pass 138 (because it coincides with the side of the rib 135 on which the inlet 132 is located); and a downstream pass 139 (because it coincides with the side of the rib 135 on which the outlet 134 is located). Additionally, it will be appreciated that between the upstream pass 138 and the downstream pass 139, the switchback 131 may be described as having a turn-section 142. The turn-section 142 may define a turn of approximately 180°.

The cooling chamber 130 may have a planar configuration that is aligned with and contained within the platform 110 or a specific region of the platform 110. As used herein, an “outboard profile” of the cooling chamber 130 refers to the profile as seen from a position outboard of the platform 110, which, it will be appreciated, is the perspective shown in FIGS. 7 and 9 through 11. It will be appreciated that in certain embodiments the cooling chamber 130 may be offset from a curved surface, such as a platform 110 having a topside 113 that includes an area of more pronounced curvature. In certain embodiments, the outboard profile of the cooling chamber 130 may be that of a quadrilateral, i.e., have four linear sides. The rib 135, as shown, may be linear in configuration. In certain embodiments, the outboard profile of the cooling chamber 130 is a parallelogram. More specifically, the outboard profile of the cooling chamber 130 may be that of a square, a rhombus, or a rectangle.

As shown most clearly in FIG. 8, the platform 110 includes a planar topside 113. (Note that “planar,” as used herein, means approximately or substantially in the shape of a plane. For example, one of ordinary skill in the art will appreciate that a platform is configured to have an outboard surface that is slight curved and convex, with the curvature corresponding to the circumference of the turbine at the radial location of the rotor blades. As used herein, this type of platform shape is deemed planar, as the radius of curvature is sufficiently great to give the platform a flat appearance.) The cooling chamber 130 may include a planar ceiling 168 that is just inboard of the topside 113 of the platform 110, as well as a planar floor 169 radially offset from the ceiling 168. The radial height of the cooling chamber 130 may be described as the radial offset between the ceiling 168 and the floor 169. As illustrated, in preferred embodiments, the radial height of the cooling chamber 130 is substantially constant. The rib 135 extends from the floor 169 to the ceiling 168 of the cooling chamber 130.

The quadrilateral profile of the cooling chamber 130 may be described as including a first pair and a second pair of opposing sides or edges, each pair including two edges of the quadrilateral that oppose each other across the cooling chamber 130. The first pair of opposing edges includes a first edge 151 and a second edge 152, and the second pair of opposing edges includes a third edge 153 and a fourth edge 154.

In certain preferred embodiments, the inlet 132 and the outlet 134 are positioned along the first edge 151 of the cooling chamber 130, and, between the inlet 132 and the outlet 134, a first end 157 of the rib 135 may be disposed that separates the inlet 132 from the outlet 134. From the first end 157, the rib 135 extends toward the second edge 152 of the cooling chamber 130, but terminates at a location short of the second edge 152. That termination point will be referred to herein as the second end 158 of the rib 135. That is, the second end 158 of the rib 135 is offset a distance from the second edge 152, thereby forming the turn-section 142 that redirects the flow of coolant toward the outlet 134. The rib 135, as stated, is canted with respect to the cooling chamber 130. As illustrated in FIG. 7, the cant of the rib 135 may be relative to the longitudinal axis of the cooling chamber 130. In a preferred embodiment, the rib 135 is canted such that a channel width of the upstream pass 138 decreases at a linear rate as the upstream pass 138 extends from the inlet 132 to the second end 158 of the rib 135. Further, the rib 135 may be canted such that a channel width of the downstream pass 139 decreases at a linear rate as the downstream pass 139 extends from the second end 158 of the rib 135 to the outlet 134. The channel width of the downstream end of the upstream pass 138 may be just greater than a channel width of an upstream end of the downstream pass 139. It will be appreciated that, in a preferred embodiment, the rib 135 is canted toward the third edge 153 such that, as the rib 135 extends from the first edge 151 toward the second edge 152, the distance between the rib 135 and the third edge 153 decreases while a distance between the rib 135 and the fourth edge 154 increases.

The angle or cant of the rib 135 may be described by the relationship it maintains with respect to the longitudinal axis of the cooling chamber 130. It will be recognized that, in the case when the third 153 and fourth edges 154 are parallel, a reference line that extends through the midpoints between the third edge 153 and fourth edge 154 is the longitudinal axis of the cooling chamber 130, which is illustrated as longitudinal axis reference line 159 in FIG. 7. In certain preferred embodiments, the angle 176 the rib 135 defines with the longitudinal axis reference line 159 of the cooling chamber 130 is between 0° and 60°. More preferably, the angle 176 defined between the rib 135 and the longitudinal axis reference line 159 of the cooling chamber 130 is between 0° and 30°.

As shown in FIG. 7, the coolant path defined by the switchback 131 may be described as including: a) an inlet channel width 160, which represents the channel width of the switchback 131 at the inlet 132, b) a pre-turn channel width 161, which represents the channel width of the switchback 131 between the second end 158 of the rib 135 and the third edge 153, c) a post-turn channel width 162, which represent the channel width of the switchback 131 between the second end 158 of the rib 135 and the fourth edge 154, and d) an outlet channel width 163, which represents the channel width of the switchback 131 path at the outlet 134. The ever narrowing channel includes a configuration in which the inlet channel width 160 is greater than the pre-turn channel width 161, the pre-turn channel width 161 is greater than the post-turn channel width 162, and the post-turn width 162 is greater than the outlet channel width 163. As further shown in FIG. 7, between the pre-turn channel width 161 and the post-turn channel width 162, the switchback 131 includes the turn-section 142, within which a turn-section channel width 164 represents a channel width of the switchback 131 between the second end 158 of the rib 135 and the second edge 152 of the cooling chamber 130. According to an embodiment of the present application, the ever narrowing channel of the switchback 131 includes a configuration in which the turn-section channel width 164 is less than the pre-turn channel width 161 and greater than the post-turn channel width 162. The ever narrowing channel along both of the flanks of the rib 135 may further be described as including: the channel width of the switchback 131 decreasing at a constant linear rate between the inlet channel width 160 and the pre-turn channel width 161, and the channel width of the switchback 131 decreasing at a constant linear rate between the post-turn channel width 162 and the outlet channel width 163.

As described, the cooling passages within turbine blades may be supplied with coolant in a variety of ways. Typically, cooling passages either receive coolant via internal passages that connect to a coolant source through the root of the blade or may be supplied with coolant through a connection with the shank cavity. Unless otherwise stated herein, the present application should not be limited to any specific method or configuration for delivering coolant to the inlet 132 or removing coolant from the outlet 134 of the cooling chamber 130.

It will be appreciated that turbine blades that are cooled via the internal circulation of a coolant typically include an interior cooling passage 116 that extends radially outward from the root, through the platform region, and into the airfoil, as described above in relation to several conventional cooling designs. It will be further appreciated that certain preferred embodiments of the present invention may be used in conjunction with conventional coolant passages to enhance or enable efficient active platform cooling, and that aspects of the present invention may be discussed in connection with one common design, such as an interior cooling passage 116 having a winding or serpentine configuration, though the aspect is not so limited in its application. As depicted in the figures, the serpentine path of the interior cooling passage 116 is typically configured to allow a one-way flow of coolant and includes features that promote the exchange of heat between the coolant and the surrounding airfoil 102. In operation, a pressurized coolant, which typically is compressed air bled from the compressor (though other types of coolant, such as steam, also may be used with embodiments of the present invention), is supplied to the interior cooling passage 116 through a connection formed through the root 104. The pressure drives the coolant through the interior cooling passage 116, and the coolant convects heat from the surrounding walls.

As the coolant moves through the cooling passage 116, it will be appreciated that it loses pressure, with the coolant in the upstream portions of the interior cooling passage 116 having a higher pressure than coolant in downstream portions. As discussed in more detail below, this pressure differential may be used to drive coolant across or through cooling passages formed in the platform. It will be appreciated that the present invention may be used in rotor blades 100 having internal cooling passages of different configurations and is not limited to interior cooling passages having a serpentine form. Accordingly, as used herein, the term “interior cooling passage” or “cooling passage” is meant to include any passage or hollow channel through which coolant may be circulated in the rotor blade. As provided herein, the interior cooling passage 116 of the present invention extends to at least to the approximate radial height of the platform 116, and may include at least one region of relatively higher coolant pressure (which, hereinafter, is referred to as a “region of high pressure” and, in some cases, may be an upstream section within a serpentine passage) and at least one region of relatively lower coolant pressure (which, hereinafter, is referred to as a “region of low pressure” and, relative to the region of high pressure, may be a downstream section within a serpentine passage).

As illustrated in FIGS. 9 and 10, a high-pressure connector 171 may be configured to connect the inlet 132 to a high-pressure coolant region of the interior cooling passage 116, and a low-pressure connector 172 may be configured to connect the outlet 134 to a low-pressure coolant region of the interior cooling passage 116. In operation, the pressure differential between the high-pressure region and the low-pressure region drives the coolant through the cooling chamber 130. That is, the high-pressure connector 171 extracts a portion of the coolant from the interior cooling passage 116, which is used within the cooling chamber 130 to remove heat from the platform 110 and then is returned via the low-pressure connector 172 to the interior cooling passage 116 where is may be used further to cool the rotor blade.

In other cases, as illustrated in FIG. 11, the inlet 132 may be supplied with coolant via a connector to an interior cooling channel 116 (such as the high-pressure connector 171) while the outlet 134 fluidly communicates with a plurality of film cooling ports or surface ports 175 that are formed on the surface of the platform 110. In one preferred embodiment, as illustrated, the surface ports 175 are positioned along the pressure side slashface 126. In other embodiments, the surface ports 175 may be positioned on the suction side slashface 122.

The present application thereby describes a two pass serpentine or switchback coolant path for use in the platform of a turbine rotor blade that includes an angled or canted rib that promotes more evenly distributed cooling. Referring to FIG. 12, it will be appreciated that the canted rib creates a decreasing cross sectional coolant flow area as the flow distance through the coolant path increases. Specifically, FIG. 12 provides a graphical representation of “Flow Parameters” versus “Total Flow Distance Through Switchback”. As shown, the “Cross Sectional Flow Area” linearly decreases due to the canted rib. The decreasing coolant flow area causes the velocity of the coolant to increase, which causes the “Heat Transfer Coefficient” of the coolant to increase. This increase counters the loss in cooling effectiveness that stems from a rise in the “Coolant Temperature” that occurs as the coolant absorbs heat moving along the coolant path. This results in an approximately constant “Heat Transfer Coefficient” as the coolant moves from one end of the coolant path to the other, which promotes more even cooling through the platform, which discourages or prevents the development of hotspots that quicken degradation of the component.

More specifically, by angling the rib between the two passes of the switchback, the cross sectional area is constantly decreasing as the coolant flows through the path. Since the mass flow rate of the coolant is constant, the decreasing area must in turn create a greater velocity. Since duct flow heat transfer coefficients are greatly influenced by fluid velocity, this creates an increasing HTC as the fluid travels through the serpentine. It will be appreciated that, because the coolant is increasing in temperature as it travels along the switchback and picks up heat from the rotor blade, the coolant becomes less able to cool the downstream portions of a typical coolant path. However, the present application describes a way in which this loss of coolant effectiveness due to temperature rise may be offset (via the increase in heat transfer coefficient due to the increased velocity) so that a relatively constant heat transfer rate is maintained through the length of the coolant path, as opposed to a decreasing one. As one of ordinary skill in the art will appreciate, for lower flow applications where convection heat transfer coefficients are low, embodiments of the present application allow for greater heat transfer with the same amount of flow. This may allow the usage of a switchback core in certain low flow applications where before it could not due to flow limitations. In other applications, the flow rate can be reduced when changing from a constant cross sectional area core versus the proposed design since the flow is used more efficiently, which, in regard to turbine engines, translates into increases in engine efficiency. Another benefit is that, in some cases, turbulators can be eliminated, which produce undesirable high frictional losses in serpentine cores. In addition, the total area of the entire two pass switchback may be unchanged, with the only modification being the canting of the rib, which allows greater cooling without increasing the size of the coolant passages or amount of coolant.

In an alternative, the above-described design features may be applied in similar fashion to the sidewall region of a stator rotor blade. FIG. 13 illustrates a side view of a turbine stator blade showing the positioning of cooling configuration according to an alternative embodiment of the present invention; and

FIG. 14 illustrates a top with partial cross-sectional view of a sidewall of a turbine stator blade 180 having a cooling configuration according to an alternative embodiment of the present invention. The stator blade 180 may include an airfoil 182 that juts inboard from an attachment with the surrounding stationary structure of the turbine section of the combustion engine. At an inboard edge of the airfoil 182, stator blade 182 may include a sidewall 184 that defines the inner radial edge of the working fluid flow path through the turbine. It will be appreciated that the sidewall 184 is similar in shape to the platform 110 of the rotor blade 100. The sidewall 184 may include a cooling chamber 130 having substantially the same features as discussed above. It will be appreciated that, as shown, the cooling chamber 130 of the sidewall 184 may have an inlet connector 185 that fluidly communicates with an inlet 132 of the cooling chamber 130, as well as an outlet connector 186 that fluidly communicates with an outlet 134 of the cooling chamber 130. The cooling chamber 130 of the sidewall 184 may have a rib 135 that is angled or canted as discussed above, which may result in an ever-narrowing upstream 138 and downstream pass 139.

As one of ordinary skill in the art will appreciate, the many varying features and configurations described above in relation to the several exemplary embodiments may be further selectively applied to form the other possible embodiments of the present invention. For the sake of brevity and taking into account the abilities of one of ordinary skill in the art, all of the possible iterations is not provided or discussed in detail, though all combinations and possible embodiments embraced by the several claims below or otherwise are intended to be part of the instant application. In addition, from the above description of several exemplary embodiments of the invention, those skilled in the art will perceive improvements, changes, and modifications. Such improvements, changes, and modifications within the skill of the art are also intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof. 

We claim:
 1. A cooling arrangement in one of a sidewall of a stator blade and a platform in a rotor blade in a turbine of a combustion turbine engine, the cooling arrangement comprising: a cooling chamber configured to pass coolant from an inlet to an outlet; and a rib positioned within the cooling chamber, the rib partially dividing the cooling chamber so to form a switchback; wherein the rib is canted with respect to the cooling chamber such that the switchback comprises an ever narrowing channel.
 2. The cooling arrangement according to claim 1, wherein ever narrowing channel comprises a channel that narrows at a constant rate as the channel extends from the inlet to the outlet of the cooling chamber.
 3. The cooling arrangement according to claim 1, wherein the ever narrowing channel comprises a channel that narrows at a constant rate along both flanks of the rib.
 4. The cooling arrangement according to claim 3, wherein the switchback comprises a pass positioned on each flank of the rib: an upstream pass disposed on a flank of the rib that coincides with the inlet; and a downstream pass disposed on a flank of the rib that coincides with the outlet; and wherein, between the upstream pass and the downstream pass, the switchback comprises a turn section that defines a turn of approximately 180°.
 5. The cooling arrangement according to claim 4, wherein the cooling chamber comprises a first edge and a second edge, wherein the second edge opposes the first edge across the cooling chamber; wherein the rib extends linearly between a first end, which is positioned on the first edge of the cooling chamber between the inlet and outlet, and a second end, which is offset a distance from the second edge of the cooling chamber.
 6. The cooling arrangement according to claim 5, wherein: the rib is canted such that: a channel width of the upstream pass decreases at a linear rate as the upstream pass extends from the inlet to the second end of the rib; and a channel width of the downstream pass decreases at a linear rate as the downstream pass extends from the second end of the rib to the outlet; and a channel width of a downstream end of the upstream pass is just greater than a channel width of an upstream end of the downstream pass.
 7. The cooling arrangement according to claim 1, wherein the cooling chamber comprises a planar configuration and an outboard profile of a quadrilateral; and wherein the rib is linear.
 8. The cooling arrangement according to claim 7, wherein the quadrilateral comprises a first pair and a second pair of opposing edges, each pair comprising two of the sides of the quadrilateral that oppose each other across the cooling chamber; wherein the first pair of opposing edges includes a first edge and a second edge, and the second pair of opposing edges includes a third edge and a fourth edge; and wherein the inlet and the outlet are disposed on the first edge, and, between the inlet and the outlet, a first end of the rib is positioned on the first edge.
 9. The cooling arrangement according to claim 8, wherein, from the first end, the rib extends toward the second edge, the rib terminating at a second end; wherein the second end of the rib is offset a distance from the second edge. wherein the third edge is parallel to the fourth edge; and wherein the rib is canted with respect to a direction of a longitudinal axis of the cooling chamber that is defined by midpoints defined between the third and fourth edge.
 10. The cooling arrangement according to claim 9, wherein the rib is canted toward the third edge such that, as the rib extends from the first edge toward the second edge, a distance between the rib and the third edge decreases by a linear rate while a distance between the rib and the fourth edge increases by the linear rate.
 11. The cooling arrangement according to claim 10, wherein the angle defined between the rib and the direction of the longitudinal axis of the cooling chamber is between 0° and 30°.
 12. The cooling arrangement according to claim 10, wherein the angle defined between the rib and the longitudinal axis of the cooling chamber is between 0° and 60°; wherein the switchback comprises: a) an inlet channel width, which represents the channel width of the switchback at the inlet; b) a pre-turn channel width, which represents the channel width of the switchback between the second end of the rib and the third edge; c) a post-turn channel width, which represent the channel width of the switchback between the second end of the rib and the fourth edge; and d) an outlet channel width, which represents the channel width of the switchback path at the outlet; and wherein the ever narrowing channel comprises a configuration in which the inlet width is greater than the pre-turn width; the pre-turn width is greater than the post-turn width; and the post-turn width is greater than the outlet channel width.
 13. The cooling arrangement according to claim 12, wherein, between the pre-turn channel width and the post-turn channel width, the switchback comprises a turn-section within which a turn-section channel width represents a channel width of the switchback between the second end of the rib and the second edge of the cooling chamber; wherein the ever narrowing channel comprises a configuration in which the turn-section channel width is less than the pre-turn channel width and greater than the post-turn channel width.
 14. The cooling arrangement according to claim 12, wherein the ever narrowing channel along both of the flanks of the rib comprises: the channel width of the switchback decreasing at a constant linear rate between the inlet channel width and the pre-turn channel width; and the channel width of the switchback decreasing at a constant linear rate between the post-turn channel width and the outlet channel width.
 15. The cooling arrangement according to claim 9, wherein the outboard profile of the cooling chamber comprises a parallelogram.
 16. The cooling arrangement according to claim 9, wherein the one of the platform and the sidewall comprises a planar configuration and wherein the cooling chamber comprises a planar configuration that is aligned with the planar configuration of the one of the platform and the sidewall and contained therein.
 17. The cooling arrangement according to claim 9, wherein the one of the platform and the sidewall comprises a planar topside; wherein the cooling chamber comprises a planar ceiling that is just inboard of the topside and a planar floor radially offset from the ceiling, and wherein a radial height of the cooling chamber comprises the radial offset between the ceiling and the floor; and wherein the radial height of the cooling chamber is constant.
 18. The cooling arrangement according to claim 9, wherein the cooling arrangement is disposed in the platform of the rotor blade; wherein the rotor blade includes an interior cooling passage formed therein that extends from a connection with a coolant source at the root to the approximate radial height of the platform, wherein, in operation, the interior cooling passage comprises a high-pressure coolant region and a low-pressure coolant region; further comprising: a high-pressure connector that connects the inlet to the high-pressure coolant region of the interior cooling passage; a low-pressure connector that connects the outlet to the low-pressure coolant region of the interior cooling passage.
 19. The cooling arrangement according to claim 9, wherein the cooling arrangement is disposed in the platform of the rotor blade; wherein the rotor blade includes an interior cooling passage formed therein that extends from a connection with a coolant source at the root to the approximate radial height of the platform; further comprising: a connector that connects the inlet to the interior cooling passage; and a plurality of film cooling ports that fluidly communicate with the outlet.
 20. A cooling arrangement in a platform of a rotor blade in a turbine of a combustion turbine engine, the cooling arrangement comprising: a cooling chamber configured to pass coolant from an inlet to an outlet; and a rib positioned within the cooling chamber, the rib partially dividing the cooling chamber so to form a switchback; wherein the rib is canted with respect to the cooling chamber such that the switchback comprises an ever narrowing channel.
 21. A cooling arrangement in a sidewall of a stator blade in a turbine of a combustion turbine engine, the cooling arrangement comprising: a cooling chamber configured to pass coolant from an inlet to an outlet; and a rib positioned within the cooling chamber, the rib partially dividing the cooling chamber so to form a switchback; wherein the rib is canted with respect to the cooling chamber such that the switchback comprises an ever narrowing channel. 